BigInteger(大整数）

java.math.BigInteger。 父类：Number

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常用构造方法

构造方法：BigInteger(String val)
public class Main {
    public static void main(String[] args) throws ParseException {
    	//构造BigInteger
        BigInteger bigInteger = new BigInteger("1234442314321423141");
    }
}

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常用方法

public class Main {
    public static void main(String[] args) throws ParseException {
        BigInteger num1 = new BigInteger("123443214");
        BigInteger num2 = new BigInteger("123443214");
        BigInteger result = num1.add(num2);
        System.out.println(result);

    }
}

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BigDecimal(大浮点数）

java.math.Biginteger。父类：Number

BigDeciaml 精度无限

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常用构造方法

构造方法：BigDecimal(String val)
//构造大浮点数
BigDecimal a = new BigDecimal("3.1423431243241242134132");

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常用方法

public class Main {
    public static void main(String[] args) throws ParseException {
       BigDecimal num1 = new BigDecimal("1.23434324324324");
       //小数点向右移动三位
       BigDecimal num2 = num1.movePointRight(3);
       System.out.println(num2);
    }
}

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DecimalFormat(数字格式化)

java.text.DecimalFormat 包下
数字转化成特定格式的字符串

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public class Main {
    public static void main(String[] args) throws ParseException {
      DecimalFormat df = new DecimalFormat("###,###.##");
      //格式化数字，数字字面量，转成 String
      String s = df.format(12343214213412.123);
      //输出：12,343,214,213,412.12
      System.out.println(s);
    }
}